With the proliferation of computers and computer networks into all aspects of business and daily life—financial, medical, education, government, and communications—the concern over computer security is growing. A major issue in computer security is the problem of computer viruses. A computer virus is generally a manmade destructive computer program or code that is loaded onto a computer system without the knowledge of the user. The computer virus is often a self-replicating program that copies itself and infects other programs and data files by modifying them or their environment. The computer virus spreads from one computer to another when an infected computer program or data file is taken to the uninfected computer, for example, by a user sending it over a network or carrying it on a portable storage medium. While some computer viruses are intentionally destructive, for example, deleting data, many other viruses are fairly benign. However, even such viruses are dangerous as they are able to access systems, potentially utilizing a large portion of the available resources and possibly shutting down an infected computer system.
Many antivirus programs have become commercially available for protection against viruses. Most commercially available antivirus programs scan computer files to look for known viruses by comparing the data of the computer file with signatures in a dictionary of known viruses that the authors of the antivirus software have identified. If some data in the computer file match a signature of a virus identified in the dictionary, the antivirus software takes one of the following actions:    attempts to repair the infected file by removing the virus from the file;    quarantines the infected file such that the file remains inaccessible to other programs and its virus can no longer spread; and,    deletes the infected file.As is evident, the signatures in the dictionary need to be updated on a regular basis. The antivirus software typically examines files when a computer's operating system creates, opens, closes, downloads, or e-mails them. Furthermore, the antivirus software is usually scheduled to scan all files on the computer's hard-drive on a regular basis. However, this still leaves a loophole for spreading a computer virus before a dictionary is updated.
With ever increasing storage capacity of portable storage devices such as CDs, DVDs, and USB memory storage keys, manual file transfer from one computer to another is substantially facilitated. Unfortunately, this also increases the risk of transferring an infected file from one computer to another.
Furthermore, the increasing storage capacity of USB memory storage keys presents a significant security challenge for large organizations. Their small size and ease of use allows unsupervised visitors or unscrupulous employees to smuggle confidential data with little chance of detection. To prevent this, some organizations—particularly government departments and larger corporations—forbid the use of USB memory storage keys, and computers are configured to disable the mounting of USB memory storage keys. Some organizations use a lower-tech security solution, disconnecting USB ports inside the computer or filling the USB ports with glue.
It would be highly desirable to overcome the drawbacks of the present technology and to increase computer security.